Typical gyrocopters are severely limited by the amount of power their engine produces. From the Rotax Operator’s Manual’s performance data tables it can be deduced that small gyrocopters need around 67 kW to fly straight and level. This leaves only around 18 kW of reserve power that can be used for manoeuvres or climbing.*
Because the Trojan’s form factor is very much the same as other tandem gyrocopters the power required for cruise will be only slightly higher considering the weight of the machine. If we assume 75 kW for cruise power required, we can quickly deduce that even the least powerful version with 170 hp/126 kW at MAUW can climb out at 1280 ft./min.*
Typical Break Specific Fuel Consumption (BSFC) Values for Otto-cycle four-stroke engines vary from 210 to 270 [g/kW.h] in the WOT condition. (BSFC will increase as the throttle is closed.) This means that a given engine will burn around 325 ml of fuel for every 1 kW of power produced for 1 hour when the throttle is wide open. (250 g equals 325 ml of mo-gas)
Remember that a more powerful engine can always produce less power with a lower power setting. The BSFC will be higher and consequently it will use a little more fuel. (Around 2 – 5 l/h) Because the engine does not work hard at these power settings the reliability is increased.
Using the calculator
1. Choose weight
Choose the wight of the aircraft using the drop-down list. Typically a small gyroplane will have an MAUW of 500 kg, the Trojan’s MAUW is 800 kg.
2. Choose power
The power will depend on the aircraft’s engine. The following table provides engines and their power output and fuel consumption at maximum power:
l/hr @ Max Power**
|Rotax 914 UL||85 / 115||28|
|Subaru 2.5 N/A||126 / 170||38|
|Subaru 2.0 T/C||150 / 200||50|
|Subaru 2.5 T/C||200 / 270||65|
3. Adjust Fuel Consumption
Adjust the fuel consumption so as to get a realistic BSFC value. BSFC values are generally higher for turbocharged engines than Naturally Aspirated.
4. Observe Climb Rate
The climb rate can be observed for the different weight and power adjustments.
BSFC: Break-specific Fuel Consumption
WOT: Wide Open Throttle, when the throttle is unchoked
MAUW: Maximum All-Up Weight
N/A: Naturally Aspirated
T/C: Turbo Charged
*climb out performance is for sea level conditions and will deteriorate at altitude.
** Approximate Values